Wheel sizes for shorter riders – Part 2

27.5 – 29er – Mullet. Which is the suitable wheel size?

Hopefully, you read the first part of my post from last week. If not, I highly recommend doing so. I was talking about the occurrence of injuries because of low cadence – hard gear pedalling and components which may prevent it. Also, I established my credentials that hopefully, enable me to rumble about things like that. In this second part, I will write about the results of my 3 months of testing of 3 different wheel configurations.

Being a racer and coach, hard facts and numbers are everything for me. I did all the testing back to back, using the different bikes on the same track on the same day. In 4 MTB parks, 10 familiar enduro tracks were used at pretty much race pace. Time recorded by an action camera mounted on the handlebar. Bikes were not tested on pure, dedicated climbing tracks. Both test bikes are 140 – 160 mm travel and with these types of MTBs you tend to just get it done on the uphill bits and you are not aiming for being the best climber in town.

I can’t publish a paper of my testing because I could not use the same models for my ‘experiment’. For 27.5” bike I used my own race bike for 2 years, a Giant Hail Advanced 0 with 160 mm travel. For 29”, I used the demo bike, a Rocky Mountain Instinct with 140 mm travel. For Mullet, I used the rear wheel from my 27.5” seamlessly fitted into the 29”er. However, my aim was not to write an article or publish a paper but to test the handling and manoeuvrability of different wheel sizes for my clients and possibly settle for a different bike for myself. I found the results so interesting, I thought I should share with TFB’s followers. So please, read it with this in your mind and refrain picking on different tyre compounds, geometries, or brake brands etc.

Handling differences of a 29”er compared with my usual 27.5” wheel set up:

29”er felt very measured, almost as the trail features were coming up in slow motion. I like to spin, so I had to shift more often otherwise stuck in a hard gear too long out of corners. I was game to enter rock gardens faster because the bigger wheels felt they were rolling over rocks with more ease. I had to be more aggressive with the initiation of the turns but once the front wheel was in the corner, it was tracking with more stability & I had to do fewer fine corrections. Being 164 cm, the rear wheel zipped on my bum a couple of times on very steep sections, which is unpleasant and sometimes frighting, even though I don’t need to worry about jiggling man parts 😊.  Also, on very tight turns, I really had to swing my body sideway to make sure I will make the corner. On high speed jumps (talking about over 40 km/h) the front end was rotating forwards more than I preferred but assumed that with a change in body position, I could get used to it over time.

Time wise, the 27.5” and 29”er were in the same second on 4 trails out of the 10. For Riverina locals: ‘Generator’ & top half of ‘Flow Town’ at Falls Creek and ‘Short Course DH’ & ‘Don’t Be a Hero’ at Beechworth. These 4 trails have combination of big, smooth rock roll overs, fast open sections, and some quick direction changes.

The 27.5” was faster on two trails, ‘Glock to Home Run’, which is the most technical descend in Albury. The other one is ‘High Voltage’ at Falls Creek. Both trails are very busy, constantly corners and rock features are coming up.

The 29”er was faster on 4 trails. ‘Vortex’ and bottom half of “Flow Town’ at Falls Creek and ‘Rock n Roller’ and ‘Hunchy loop’ at Wodonga. These trails are more open and high speed. Also, the elevation is greater so, instead of pedalling out of the corners, often enough just let the brake off earlier and the bike picks up the speed instantly because of the steep terrain. I could get off the brakes earlier, because the more stable front wheel feeling in the corners.

So, both wheel sizes scored well and have pros and cons but you, the reader, probably knew this already. Numerous articles have been written about the two wheels sizes, although not too many from a short rider, under 172 cm perspective.

And then the Mullet testing:

I was planning to get a new enduro race bike, but I was not overly sold on the 29er. I checked the hub and axle width and my 27.5” rear wheel smoothly fitted into the 29er, creating a Mullet. It was mid – March and the Covid – 19 travel restriction arrived, with the closure of the Falls Creek MTB park. It reduced my testing trails to 5 but still left me with a good variety of tracks to test on.

The handling of the Mullet was the best of both worlds. The stable, almost slow motion feeling of the 29er had been kept but without the sluggishness. I have an aggressive riding style with good core strength, to keep the bike fast and leaned in a corner but don’t have the acceleration leg strength of a man. However, with the 27.5” rear wheel I do not have to, as the exit speed stayed the same lively set up that I was used to. Although I had the same branded cassette with the same gear ratio on both wheel sizes, I always felt between two gears with the 29er. Either too much spinning or too low cadence. Of course, this can be fixed with a different front chainring, but can take toll on the hardest gear set up. Anyway, this feeling was completely eliminated with the 27.5” rear wheel. Other positive handling point was jumping. I always felt the 29er too long on the jumps and had to initiate the bike press earlier to get the desired height or length. Certainly, with a changed riding style, I could get used to that but the 27.5” rear wheel flicks around with more ease; so why would I?

Mullet timing:

All right, this wheel set up feels good but what does the time say? The Mullet was FASTEST on all 5 trails. The time was between 2 & 15 seconds faster, depending on the length of the test tracks. On the ‘Short Course DH’, a bit longer than 2 minutes trail the Mullet was 7 (!) seconds quicker than the two other wheel sizes. This is when the video timing comes in handy. I put the onboard footage of the 29er and the Mullet side by side and started the video together to work it out where I gained this huge advantage. This Beechworth track has a looooong rock garden. Maybe 400 m long. Starts with small rocks and ends up with step downs while the rider needs to change direction to avoid boulders and trees. I advanced around 5 seconds in that rock garden because I could manoeuvre the smaller rear wheel around. Another 2 seconds was taken off the clock in 3 fast but flat corners with jumpable rollers between them. I could accelerate out of the corners quicker and keep my speed up to be able to jump the rollers.

Decision made, I will have a Mullet as my new enduro race bike! Being a reasonably new phenomenon, the next question raised. Do I turn a 29er or a 27.5” bike into a Mullet? What different parts I need to keep the geometry? Do I need to set up my suspension differently?

My findings will be in part 3. Stayed tuned for next week…

 

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